The present invention relates to a method of forming an amorphous silicon film on a base, e.g., a conductive substrate.
Conventional glow discharge as one of the standard methods of forming an amorphous silicon film on a conductive substrate is performed as follows. A raw material gas such as SiH.sub.4 is supplied to a vacuum chamber as a reaction vessel which is maintained at a vacuum, and a DC or AC voltage or an electromagnetic wave is applied to an electrode opposing the conductive substrate in the vacuum chamber, thereby effecting glow discharge to generate a plasma. The plasma containing ions and radicals is brought into contact with the conductive substrate disposed in the vacuum chamber, and an amorphous silicon film is formed on the conductive substrate.
However, according to this conventional method, a plasma containing a large number of silicon radicals cannot be easily generated unless high power is applied. When the power applied falls within the range between several tens of watts to several hundreds of watts, the deposition rate of the amorphous silicon film on the conductive substrate is low. A maximum rate is at best 3 .mu.m/hour, resulting in inconvenience. Therefore, it takes at least six hours to form an amorphous silicon film to a thickness of 20 .mu.m. Thus amorphous silicon photoconductors cannot be manufactured on a high-speed mass production line. However, when higher power is applied to increase the deposition rate of the amorphous silicon film, the silicon powder produced by expitaxial reaction in the raw material gas clogs the exhaust system of the manufacturing apparatus. In addition to this disadvantage, when the power is increased, the amount of Si.dbd.H.sub.2 bonds becomes higher than that of Si--H bonds, so that the photoconductivity of the resultant amorphous silicon film is degraded.